% PT_BLK_ALLOC_DECODER(3)

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# NAME

pt_blk_alloc_decoder, pt_blk_free_decoder - allocate/free an Intel(R) Processor
Trace block decoder


# SYNOPSIS

| **\#include `<intel-pt.h>`**
|
| **struct pt_block_decoder \***
| **pt_blk_alloc_decoder(const struct pt_config \**config*);**
|
| **void pt_blk_free_decoder(struct pt_block_decoder \**decoder*);**

Link with *-lipt*.


# DESCRIPTION

A block decoder decodes raw Intel Processor Trace (Intel PT) into a sequence of
blocks of instructions described by the *pt_block* structure.  See
**pt_blk_next**(3).

**pt_blk_alloc_decoder**() allocates a new block decoder and returns a pointer
to it.  The *config* argument points to a *pt_config* object.  See
**pt_config**(3).  The *config* argument will not be referenced by the returned
decoder but the trace buffer defined by the *config* argument's *begin* and
*end* fields will.

The returned block decoder needs to be synchronized onto the trace stream before
it can be used.  To synchronize the decoder, use **pt_blk_sync_forward**(3),
**pt_blk_sync_backward**(3), or **pt_blk_sync_set**(3).

**pt_blk_free_decoder**() frees the Intel PT block decoder pointed to by
*decoder*.  The *decoder* argument must be NULL or point to a decoder that has
been allocated by a call to **pt_blk_alloc_decoder**().


# RETURN VALUE

**pt_blk_alloc_decoder**() returns a pointer to a *pt_block_decoder* object on
success or NULL in case of an error.


# EXAMPLE

~~~{.c}
    struct pt_block_decoder *decoder;
    int errcode;

    decoder = pt_blk_alloc_decoder(config);
    if (!decoder)
        return pte_nomem;

    errcode = decode(decoder);

    pt_blk_free_decoder(decoder);
    return errcode;
~~~


# SEE ALSO

**pt_config**(3), **pt_blk_sync_forward**(3), **pt_blk_sync_backward**(3),
**pt_blk_sync_set**(3), **pt_blk_get_offset**(3), **pt_blk_get_sync_offset**(3),
**pt_blk_get_image**(3), **pt_blk_set_image**(3), **pt_blk_get_config**(3),
**pt_blk_time**(3), **pt_blk_core_bus_ratio**(3), **pt_blk_next**(3)